-LRB- CNN -RRB- -- The major tunnel between Windsor , Ontario , and Detroit was scheduled to reopen at 5 p.m. ET Thursday following a shutdown because of a bomb threat , Windsor police said .

Police `` fully inspected '' the tunnel before reopening it , Windsor authorities said .

The bomb threat led to traffic backups as drivers on both sides of the border were rerouted .

Employees at the Detroit-Windsor Tunnel received an anonymous phone call around 12:30 p.m. from someone saying there was a bomb in the tunnel , Sgt. Matthew D'Asti with Windsor police told HLN .

Authorities were working together on both sides of the border to investigate and search the tunnel for any possible device , D'Asti said .

Neal Belitsky , president and CEO of Detroit-Windsor Tunnel , said the threat was called in to the Canadian side .

Authorities treated the matter `` as a nonspecific , anonymous bomb threat , '' said D'Asti . The tunnel was evacuated .

The tunnel is one of two international crossings between the cities of Windsor and Detroit .

Traffic was being routed to the other , a bridge about two miles away .

Approximately 27,000 to 29,000 vehicles pass daily through the tunnel , which opened in 1930 .

The Coast Guard said it set up a safety zone in the Detroit River in order to keep vessels away from the tunnel .

CNN 's Chandler Friedman , Devon Sayers and Michael Martinez contributed to this report .

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NEW : Windsor police reopening `` fully inspected '' tunnel

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The call came from the Canadian side , officials say

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An anonymous caller reported a bomb in the Detroit-Windsor Tunnel

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The tunnel was evacuated ; no bomb has been found , an official tells HLN